MORPHOLOGICAL AND GENETIC-VARIATION IN THE ANTARCTIC LIMPET NACELLA-CONCINNA (STREBEL, 1908)

Samples of the Antarctic limpet, Nacella concinna (Strebel, 1908), were collected from four sites in the South Orkney Islands and from Stromness in South Georgia during 1988. At three South Orkney sites, both littoral and sub-littoral samples of limpets were taken. Shell dimensions were measured and littoral and sub-littoral limpets were shown to have significantly different shell shapes. Foot and digestive gland tissues were subjected to electrophoresis and five polymorphic loci (Es-1, Icd-1, Icd-2, Gpi, Got-1 and Pgm-1) and two monomorphic loci (Es-2 and Got-2) were scored. Genetic identities between littoral and sub-littoral forms and also between sites were calculated. At the loci scored, the littoral and sub-littoral forms were virtually identical and this suggests that the shell shape differences between the forms are the result of environmentally induced phenotypic plasticity. However, significant genetic differences and some morphological differences were apparent between the sample of limpets from South Georgia and all other sites. Genetic identity values suggested that the South Georgia and South Orkney N. concinna are geographically separated populations of a single species rather than distinct sub-species.